A recent study into one of the fruit industry's most divisive topics has received a lukewarm response from the European Food Safety Authority (EFSA), criticizing its methodology and conclusions.

The study from Guarnaccia et al claims the fungal pathogen that causes citrus black spot (CBS) - a phytosanitary threat of great concern to EU growers - is present in domestic gardens in Portugal, Malta and Italy, however the disease itself is not.

In its review of the study, the EFSA questioned why the pathogen Phyllosticta citricarpa was only found in leaf litter, while also raising concerns about how sites were chosen and selected.

"The authors only report findings of P.  citricarpa and P. paracitricarpa from leaf litter, but no positive detection from living plants (fruit, leaves or twigs) was obtained in the same plants," an EFSA panel said in the review.

"However, since leaf litter only originates from living leaves and since P. citricarpa has not been shown to infect or colonise dead leaves (Truter et al., 2007), the P.  citricarpa must have infected the above living leaves.

"Thus, the claim that there was no CBS disease even where the pathogen was present is not supported by the results presented."

The EFSA described the sampling procedure as "inconsistent and not statistically based".

"No explanation is given for how the CBS disease surveys were conducted. Without properly constituted disease surveys, there is little support for the conclusion that P. citricarpa did not lead to disease," the authority said.

The EFSA said the findings confirmed its own predictions made in 2008 that the pathogen could establish itself in some citrus-growing regions in Europe, and concluded there appeared to be two independent introductions into Europe with the one in Portugal being different to the one present in Malta and Italy.

Photo: P. Barkley, Biological and Chemical Research Institute, Bugwood.org 

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